CHICAGO -- It took more than two periods and the ejection of their best player for the Washington Capitals to get fully invested in a game that began at the early hour of 11:30 a.m. Central time.

But when they awoke, Nicklas Backstrom and his teammates finally looked like the NHL's best team. Backstrom scored two of Washington's four unanswered goals, including one late in overtime, to defeat the Chicago Blackhawks, 4-3, in a game that may well have been a preview of this year's Stanley Cup finals.

Thanks to another controversial hit by two-time MVP Alex Ovechkin, however, Backstrom's end-to-end rush in the extra session wasn't the focus after the league-leading Capitals humbled the league's third-ranked team before a national television audience and a disgusted capacity crowd at United Center.

Ovechkin was ejected for shoving Brian Campbell at 12 minutes 16 seconds of the first period, sending the Blackhawk back-first into the boards behind the Chicago net.

Campbell had just reversed the puck when Ovechkin, who outweighs the defenseman by 34 pounds, shoved him on his side, causing Campbell to lose his balance and hit the boards with a thump.

Campbell lay down for several minutes as he was attended to by the Chicago training staff; Ovechkin, who immediately gestured toward the fallen Blackhawk as if to apologize, was first sent to the penalty box, then escorted from the rink by a linesman after being assessed five minutes for boarding and his third misconduct of the season. Campbell did not return to the game and will be "out for a bit" according to Blackhawks Coach Joel Quenneville.

It was unclear after the game whether Ovechkin would face further punishment from the NHL, but the league tends to come down harder on players with prior history. And with Ovechkin there's plenty to consider. His first ejection of 2009-10 came Nov. 25 against Buffalo when he was assessed five minutes for boarding Sabres agitator Patrick Kaleta. Five days later, he was tossed in Raleigh, N.C., after being given five minutes for kneeing the Hurricanes' Tim Gleason. Ovechkin also was suspended by the NHL for two games for the hit on Gleason.

"It was not a hard hit," Ovechkin said. "I just little push him . . . but I don't think it has to be five minutes. I've seen the replay a couple of times. He fell bad."

Coach Bruce Boudreau added: "I thought it was a push from the side [where] he could see his numbers. It wasn't dead on into the boards. Campbell was turning. Alex didn't extend his arms. He just pushed him. Sometimes you don't realize how strong Alex is."

With Washington already down a man because of Ovechkin's penalty, Alexander Semin was sent off for goaltender interference, and Jonathan Toews wasted little time capitalizing. The Chicago captain netted his second goal of the game, beating José Theodore on a rebound.